Quantitative Investigations of Leaf Pigments From Their Inception in Buds Through Autumn Coloration to Decomposition in Falling Leaves

Pigments in hazel (Corylus americana), aspen (Populus tremuloides), and pin oak (Quercus ellipsoidalis) leaves were measured from their inception in buds to development of a summer maximum, and through the autumn coloration period to decomposition in dry falling leaves. Leaves contained generally high but varyingconcentrations of chlorophyll and carotenoid pigments throughout the summer months. The summer pigment variations among the three species are discussed in the light of the usefulness of chlorophyll content as an index of net primary productivity. During the autumn coloration period, preceding leaf desiccation and fall, chlorophyll decays rapidly, producing low levels of pheophytin with only occasional faint traces of pheophorbide and chlorophyllide during the period of most rapid chlorophyll breakdown. The levels of carotenoids begin declining at the same time as chlorophyll, but at a much slower rate. Violaxanthin disappears most rapidly, followed closely by neoxanthin. Lutein and Beta—carotene are the most stable carotenoids. Falling oak leaves, whether dropped to the ground in autumn or held on the tree throughout the winter, in spring still contain measurable amounts of letuein and Beta—carotene and low concentrations of pheophytin a. Con—current with the autumn degradation of plastid pigments in an abrupt and substantial rise in anthocyanin of oak and hazel. At leaf—fall aspen and hazel leaves are devoid of all pigments.